The invention relates to a process for treating tobacco and similar organic materials, comprising
impregnating the material with an inert organic liquid and heating it beyond the boiling point of said liquid by introducing a hot gas, whereby the liquid is evaporated while the material is expanded,
after the expansion, recovering part of the evaporated liquid while a rest is left in the material.
Such a process has been known from German OS No. 19 17 552 and German OS No. 22 03 105. In said known processes, tobacco is impregnated with liquid or vaporous inert organic compounds. During a subsequent thermal treatment with gas vapour or steam, the impregnant is evaporated, while tobacco is expanded to be disaggregated and increased in volume. To reduce to a minimum the extraction of the soluble components normally present in the tobacco under treatment, the impregnating fluid, as introduced into the tobacco, should be in the vapor state. Thus, a reduction of the required amount of impregnant is possible as well. During the tobacco expansion, its filling capacity is increased by 60 to 120%. The impregnant evaporated during the expansion is evacuated together with the gas. From the mixture, the expansion agent may be recovered. It is disadvantageous in the known process that a residue of the impregnant is left in the expanded tobacco. To remove from the latter the residual amounts, the tobacco must be stored for some time until the impregnant has volatized. Such a storage is involved with a loss of time during the tobacco treatment and corresponding storage facilities as well as means for conditioning tobacco are necessary. The residual amount removed by storage is accessible but with difficulty for its recovery.
According to U.S. Pat. No. 3,828,797, tobacco expansion is performed in that the tobacco impregnated with a volatile organic liquid is subjected to a microwave treatment. The total energy required to evaporate the expansion agent is applied by microwaves. Such an energy-rich microwave treatment is extremely difficult on the large-scale basis, because, in case of a complete evaporation of the expansion agent, the tobacco material may be easily overheated. Practically, it is impossible to dose microwave energy such as to evaporate the expansion agent in total and not to overheat the tobacco for all that. Further, energy consumption of the known process is very high. While the process may be well performed under laboratory conditions, it is hardly practicable for use on a large-scale basis.
It is the object of the invention to provide a process of the above mentioned kind in which the residual amount of impregnant still present in tobacco after its expansion will be shortly removed therefrom without the need of an expensive tobacco storage.